If a slightly conducting liquid enters a chamber containing a bath gas through a small bore metal tube maintained at several kilovolts relative to the chamber walls it emerges as a fine spray of charged droplets. The droplets evaporate to produce, by a mechanism not yet well understood, a dispersion of ions in bath gas some of which comprise intact solute (analyte) species. A portion of this gaseous dispersion of ions passes through a small aperture into a vaccum system for analysis by a mass spectrometer. The objective of the proposed program is to develop this Electrospray Ionization (ESPI) process into a useful and convenient tool for mass spectrometric analysis of solutions containing species of biochemical importance. A further objective is to make ESPI the basis of a useful on-line interface between a Liquid Chromatograph and a Mass Spectrometer and thus to increase the effectiveness of LC-MS as a analytical tool in bio-medical research. Ultimately, there may be applications in clinical medicine as well. ESPI mass spectrometry has already proved itself to be a very soft ionization method of great analytical sensitivity but much remains to be learned about its component mechanisms and how they effect performance. The proposed program embraces investigations of: (1) the mechanics and dynamics of the electrospray process; (2) the range of solute species masses over which ESPI is effective; (3) the factors that determine the number of charges per ion; (4) the effects of solution composition on yields and identity of the ions formed; (5) methods of producing controlled fragmentation of parent ions of obtained information of identity and structure with emphasis on Surface Induced Dissociation; (6) the possible use of mobility analysis of ESPI ions as a simple and economical LC detection means; (7) the compatibility of ESPI-MS with LC in the displacement mode and with Zone Capillary Electrophoresis (ZCE).